The Solemnity of the Most Holy Trinity is somehow “artificial”, as it does not root in a biblical or historical tradition, but rather in a high-level reflection of dogmatic theology. This solemnity needed several decades to get established in the entire Latin Church around the 9th and 10th centuries. And as artificial as the solemnity itself is its original introit Benedicta sit sancta Trinitas: The composers used an existing introit (Invocavit) and adopted it for a new, non-biblical text. That is liturgy made by systematic theologians, and honestly: The new text does not really match the original melody.

After the Second Vatican Council there was a new decision made only for the liturgical year C, which we have in 2019. With Rom 5:1–5 as today’s 2nd reading, Caritas Dei became the introit in this year. In today’s order, Caritas Dei is also the regular introit for the Vigil Mass of Pentecost Sunday, while it was originally used on the Saturday after Pentecost.

Here is what I like about Caritas Dei the most: There is the melody of diffusa where you can hear the Spirit as if someone dramatically opens a bottle of oil and starts to pour it over us. The Spirit gets somehow physical here. It is not something that you learn and understand, but something that you experience in your human entirety with body and soul.

In the Western calendar Trinity Sunday became the continuation of the Easter cycle: the dogma of the Trinity presents the quintessence of the entire revelation. With Caritas Dei the mystery of Trinity is more focused on the Spirit in us, rather than Benedicta sit with a dogmatic teaching from a schoolbook. The Byzantine liturgy has established its own way to celebrate the Most Holy Trinity: Pentecost Sunday and Monday commemorate Trinity and the Spirit, binding the dogma of Trinity even closer to the Holy Spirit than the Latin liturgy does.